(a) Field of the Invention
The present invention relates to a fuel cell system, and more particularly, to a cooling apparatus for a fuel cell stack.
(b) Description of the Related Art
As known in the art, a fuel cell is a system for producing electric power through a chemical reaction of oxygen and hydrogen contained in hydrocarbon-group materials such as methanol, ethanol, and natural gas.
Recently, a polymer electrolyte membrane fuel cell (hereinafter, referred to as PEMFC) has been developed in the field of fuel cells. Since the PEMFC has excellent output characteristics, a low operating temperature, and fast starting and response capabilities, it has a wide range of applications such as a mobile power source for vehicles, a distributed power source in the home or buildings, and a small-sized power source in electronic devices. The PEMFC system typically includes a stack, a reformer, a fuel tank, and a fuel pump. The stack forms an electricity generating assembly consisting of a plurality of unit cells, and the fuel pump supplies to the reformer fuel stored in the fuel tank. The reformer reforms the fuel to create hydrogen gas, and supplies the hydrogen gas to the stack.
Accordingly, the PEMFC system supplies to the reformer the fuel stored in the fuel tank by operation of the fuel pump, and the fuel is reformed in the reformer to generate hydrogen gas. Then, the hydrogen gas is supplied to the stack. Air is also supplied to the stack through a separate pump. Subsequently, the hydrogen gas and oxygen in the air are electro-chemically reacted in the stack to generate electric energy.
In the aforementioned stack of the fuel cell system, the reaction between the hydrogen and the oxygen generates a predetermined temperature of heat, which poorly influences the stability and performance of the stack.
Also, in the conventional fuel cell systems, the air supplied to the stack is preheated to maintain an appropriate level of driving temperature in the stack. In this case, energy consumed to preheat the air reduces performance efficiency of the entire system.